Cardboard folding suitcase



FIG. 1 is a perspective view of my new and ornamental design for a cardboard folding suitcase in an open state;

FIG. 2 is a perspective view thereof in a closed state; and,

FIG. 3 is a perspective view thereof in a semi-folded state. 

The ornamental design for a cardboard folding suitcase, as shown and described. 